Use of alkali vanadates in reducing viscosity and gelation of drilling muds



Patented June 6, 1939 STATES UNITE USE OF ALKALI VANADATES IN REDUCINGVISCOSITY AND GELATION F DRILLING MUDS Milton Williams, Houston, Tex.,assignor to Standard Oil Development Company, a corporation of DelawareNo Drawing. Application October 16, 1937,

Serial No. 169,460

12 Claims.

This invention is directedjto a. drilling fluid and a method forcontrolling the viscosity thereof.

A drilling fiuid'is a system usually comprising water, colloidalmaterial, including both gel 'forming and non-gel forming types, andlarge particles suspended in the water. Ordinarily the fluid is a slurryof clay in water and may or may not contain weighting material, which isgeneral- 1y a heavy inorganic compound such as any one of various heavymetal oxides or sulfates, and

is conventionally referred to as a drilling mud.

A typical mud may weigh from 9-18# per gallon.

Of the two types of colloids present the gel forming type is the moreimportant for this type imparts the necessary properties to the drillingmud, namely, stability of suspension, thixotropy, viscosity, puresealing and gel characteristics in general. Colloids of the nongellingtype, together with the larger particles, contribute somewhat toviscosity but more particularly to the density of the mud.-

It is generally desirable in drilling practice to maintain the viscosityof the mud below about 20 centipoises as measured by the .Stormerviscoslmeter at 10 revolutions per second. Various factors tend toincrease the viscosity of the mud. Among these are the infusion into themud from the substrata of inorganic materials of a gel forming natureand the high temperatures to which the mud is subjected as the depth ofthe holeincreases. It is, therefore, the practice to add to the drillingmud agents which tend to reduce or limit the increase in the viscosityof the mud. It 'is not sufiicient that a particular agent is capable ofreducing the viscosity of a drilling mud at ordinary temperature. It isnecessary that the agent retain its viscosity reducing property afterbeing subjected to the elevated temperatures encountered in boreholesQFor this 'reason a reagent which will not effect as great a reductionatnormal temperature as another reagent may, nevertheless, be the moredesirable of the two if it possesses to agreater degree the property ofretaining its viscosity reducing power after being subjected to elevatedtemperatures.

According to the present invention the viscosity and gellingcharacteristics of a drilling mud are controlled by adding to thedrilling mud a compound of vanadium in which the vanadium is present inthe anion. Typical compounds of this nature are the alkali vanadates,including sodium orthovanadate, sodium pyrovanadate, sodium metavanadateand the pyrogenetic derivatives thereof, particularly those whichareobtained by fusing sodium metavanadate and quickly chilling the melt.Other vanadium compounds of this type are the complex compounds in whichvanadium oxide is combined with an oxide of another element in theanion, for example, sodium vanadato molybdate, sodium vanadatotungstate, etc. Likewise, various combinations of vanadium pentoxide andcaustic soda, in which the ratioof sodium to vanadium may be varied overwide limits, may be employed.

Ordinarily the treating agent in aqueous solution is added to the mud asthe latter is circulated from the storage pit to the borehole. Thetreating agent can, however, be added in solid form or it may be mixedwith clays or weighting material prior to the addition of either ofthese to the mud. Only small amounts of the treating agent need beemployed in order to effect the desired decrease in viscosity. The useof amounts varying from traces up to about 5%, by weight, of the mud iscontemplated. It is to be 'understood that an excess over the designatedupper limit has no harmful effect. r i

In the following specific examples, which are Amount added EXAMPLE IIgrams of NazCOa were dissolved in 600 cc.

tallization. A

200 cc. of a mud having an original viscosity of 145 grams at 600 R. P.M. wastreated with 1 cc. of sodium deuterovar'ladate with the followingresults:

hours the treated mud had the following viscosities: v

Stormer R. P. M. Grams driving 600.... 9a 400.... ea 2.00 49 200 39 100so EXAMPLE III Several 200 cc. samples of mud were treated with 1.0 cc.off-5% solutions of (a) sodium orthovanadate, (1)) sodium metavanadate,(c) a. solution of V205 in NaOH to make weave, and ((0 sodiumhexametaphosphate, respectively. The following were the initial effectson the viscosi- 2,160,949 vanadate was recovered from the filtrate byorys storm R M Gram driving These samples were heated on a steam chestat mass 63 C. for ,22 hours. After they became coolrthe followingvlscosities were observed: 300 12 Untreated mud 200 61 100 Grams drivingStormer R. P. M. After standing for several hours the treated mm mud hadthe following viscositles: 600 150 400 131 Stormer R. P. M. Gramsdriving 38;: 128

% 28 (a) 300 45 200 as 100 24 s00 00 400 I 300 us After being heated ona. steam bath for 72 83 After 22 hours more at 63 C. the sampleshad thefollowing viscositles:

Uiifiated mud Grams drl Stormer- R. P. M. 'l'

After a further 98 hours heating at 63 C. the following finalviscosities were measured:

Untreated mud Stormer P. M. Grams driving mass EXAMPLE IV 10 grams ofvanadium pentoxide and 10 grams of M003 were dissolved with heating injust suflicient caustic soda to effect solution. The slightly turbidliquid was filtered and the filtrate was neutralized with dilute aceticacid and evaporated to dryness. The product was sodiumhexavanadatohexamolybdate.

1 cc. of a 5% solution of this compound was added to 200 cc. of adrilling mud having an original viscosity of 145 grams at 600 R. P. M.The viscosity of the sample dropped to 129 grams at 600 R. P. M. Afterbeing heated for 72 hours in a steam chest at 63 C. the viscosity of thetreated mud was 128 grams at 600 R. P. M.

EXAMPLE V The mixture was boiled 4 hours, filtered,

heated to boiling, and a fresh portion of VaOa added. When the solutionwas apparently saturated with the oxide it was filtered. The deep orangecolored filtrate was evaporated down to a small volume at 60C., then wasplaced in a desiccator over concentrated H2804 to crystallize, yieldingsodium divanadat' tetratungstate.

200 cc. of a drilling mud having an original viscosity of 145 grams at600 R. P. M. were treated with 1 cc. of a 5% solution of this product.The

viscosity of the mud was reduced to 122 grams. After being heated for.72 hours at 63 C. the treated mud had a viscosity of grams.

EXAMPLE VI Sodium pyrovanadate was prepared by fusing amixture of 7.5grams of anhydrous V205 and 9 grams of anhydrous NazCOa, holding themelt at red heat for 2 hours, dissolvingthe melt, after cooling, inwater and precipitating the pyrovanadate, as a liquid, by adding methylalcohol. 200 cc. of a mud having an initial viscosity of grams at 600 R.P. M. and 122 grams at 400 R. P. M. was treated with 1 cc. of a 5%aqueous solution of the pyrovanadate with a resulting decrease inviscosity to 92 grams at 600 R. P. M.'

and 68 grams at 400 R. P. M. The treated sample, after being held at 63C. for 72 hours had a viscosity of 98 grams at 600 R. P. M. and 73 gramsat 400 R. P. M.

EXAMPLE VII In order to determine the effectiveness of the aboveenumerated vanadium compounds in causing the settling of sand from mudthe following experiment was carried out.

A drilling mud was mixed with 80-100 mesh sand in the proportion of twoparts by volume of mud to 1 part by volumeof sand to form a stablemixture from which sand would not settle A 100 cc. sample of thismixture was.

out. agitated vigorously and poured into a graduate in which it wasallowed to stand for five minutes. The top 10 cc. were then poured 011into a 15 cc. centrifuge tube and the sand content was determined byelutriation. The sample showed a sand content of 35.5% by volume.

This experiment was repeated withthe addition of 1 cc. of a 5% solutionof sodium hexametaphosphate to the sample. This resulted in a reductionof the sand content in the decanted portion of the sample to 6% byvolume.

The experiment was again repeated with the addition of 1 cc. of a 5%solution of sodium metavanadate to the sample. This resulted in adecrease in the sand content of the decanted portion of the sample to 1%by volume.

The nature and objects of the present invention having been thusdescribed and illustrated what is claimed as new and useful and isdesired to be secured by Letters Patent is:

1. An aqueous slurry of solid mineral matter containing in solution aninorganic compound of vanadium in which the vanadium is present in theanion.

2. A drilling fluid comprising an aqueouslslurry of clay containing insolutionan inorganic compound of vanadium in which the vanadium ispresent in the anion.

3. A drilling fluid comprising an aqueous slurry of clay containing insolution an alkali metal vanadate.

4. A drilling fluid comprising an aqueous slurry of clay containing insolution a small amount of an alkali metal metavanadate.

alkali.

5. A drilling mud comprising an aqueous slurry of clay to which has beenadded a small amount of a solution of vanadium pentoxide in caustic 6. Adrilling mud comprising an aqueous dispersion of claycontaining insolution an alkali metal vanadate metallate,'

7. A method for improving the viscosity characteristics of a drillingmud which comprises'add- 'ing thereto an inorganic compound of vanadiumin which the vanadium is present in the anion.

8. A method for improving the viscosity characteristics of a drillingmud which comprises adding thereto an alkali metal vanadate.

9. A methog for improving the viscosity characteristics of drilling mudessentially composed thereto an inorganic compound, of vanadium in whichthe vanadium is present in the anion.

10. Amethod for improving the viscosity characteristics of an aqueousslurry of clay which com: prises adding thereto a small amount of analkali metal vanadate.

- 11. A method for improving the viscosity characteristics of an aqueousslurry of clay comprising adding thereto a small amount of an alkalimetal metavanadate.

12. A method for improving the viscosity characteristics of an aqueousslurry of clay which comprises adding thereto a small amount of analkali metal vanadat/e metallate.

MILTONWILLIAMS.

of an aqueousslurry of clay comprising adding

